Fertilizing a forage crop after harvest can increase yield and quality by over 7 percent.

Manure applications to living crops have been done in forage, pasture, cereal, corn, and cover crops with varying success. Significant hurdles exist with respect to soil compaction, variable uniformity of application, nutrient use inefficiency, timing, trampling or other damage to the crop. However, the environmental and agronomic advantages of manure application into living crops are encouraging. Manure applied uniformly into living crops can reduce the use of commercial fertilizer, reduce odour and greenhouse gas emissions, trap ammonia-N, reduce overland flow, reduce leaching, and provide additional opportunities for manure application to a farm's land-base.

A toolbar that shallow injects manure in narrow bands is being evaluated for application opportunities throughout the growing season (side-dress applications in wheat, corn, application to forages and pastures, slurry seeded cover crops after cereal harvest). The results in Figure 1 are from the 2012 season where manure was applied after first-cut forage harvest and compares shallow injection to broadcast, surface banded, fertilizer equivalent and zero check.

Figure 1. Manure applied to forage after first-cut

Ammonia Loss

The choice with manure application is loss from volatilization, leaching or denitrification. Leaching and denitrification are highest with fall applied manure. Ammonia loss is highest with summer applied manure. Ammonia loss was measured using dosimeter readings. Results for 2012 (Figure 2) are consistent for losses measured over the past 4 seasons. The results show a consistent difference between "shallow injection", "surface band" and "close- to- surface splash- plate broadcast". The largest ammonia loss comes in the first 24 hours for all manure application methods and then levels off over the next few days. Rainfall in the first 24 hours after application reduces ammonia loss. Shallow injected manure had relatively lower losses, but still higher than ESN commercial nitrogen. Ammonia losses are higher with surface broadcast followed by surface banded and about 25% lower with the shallow injection. Shallow injection disturbs a narrow and of soil which allows a greater proportion of the manure to be infiltrated compared to surface band and broadcast. Losses are highest where manure rate is highest and in small ponded areas where infiltration is slower.

 

 


Figure 2. Ammonia Loss

Fertilizer nitrogen was applied mainly as ESN - a slow-release nitrogen. Where hog manure was applied, the ESN rate was doubled to reflect manure nitrogen. Where the higher rate of ESN was applied, the total ammonia loss was also double. The dosimeter readings increased after a few days in a more linear pattern.

Average of All Cuts After Application

Table 1. 2012 Yield and quality comparison of manure vs fertilizer applied to forages.
Treatment
 Yield
Adjusted for DM		 Quality
Yield + Quality
Adjusted for DM
 
tons/ac
% Change
lbs milk/ton
% Change
lbs milk/ac
% Change
Fertilizer
2.55
2.4
3,069
1.1
7,826
3.4
Splash Plate
2.64
5.7
3,038
0.1
8,020

5.8
Surface Band
2.64
5.7
3,040
0.2
8,026
5.8
Injected
2.82
11.7
3,052
0.6
8,607
12.2
Zero Check
2.49
--
3,035
--
7,557
--

Represents Oxford Centre, Salford, Brooksdale locations - 2nd, 3rd & 4th cuts

1 Milk2006 is an Excel spreadsheet that uses the forage analysis (CP, ADF, NDF and NDFd) to calculate an approximation of a balanced ration using NRC values. In the summary tables below, MILK2006 was used with all preset defaults except forage quality parameters.


Forage Yield & Quality Impacts

Manure and fertilizer was applied after first-cut harvest. Forage yields for second-, third- and fourth-cut varied greatly from location and within treatments. The highest response came with third-cut. Table 1 shows the yield and quality for each of the different application methods by cut. From all location results combined, a trend does emerge that shows the positive impact of yield from fertility - either manure or fertilizer. Yield responses between the different manure application systems were quite variable by location. The response to manure and fertilizer may have been impacted by moisture available at the different cuts. Some sites received rainfall in June which increased yield and quality by the next harvest date. In dry areas, the ammonia content of the manure may have resulted in some leave burn and may have delayed regrowth.

When quality and yield were combined in the MILK 20061 program, the impact of fertility is much clearer. There is still some variability, but fertility increased the overall combined yield and quality by 3-12%, with manure giving the larger increase. However, when comparing the treatment for second-, third- and fourth-cut individually, the yield response from third-cut ranged from 6 to 25% greater than the check treatment.

Bottom Line

A corn crop still makes the most economic use of spring applied liquid manure. When application to forages is beneficial to managing manure storage capacity, work load and crop fertility program, there is also an economic advantage to forage yield and overall forage quality. Combining the 2012 results with yield comparisons from previous years (2006-2011) overall yield increase was 2.6 percent from applying commercial fertilizer and 7.0 percent from applying manure compared to no added fertility. Quality increase over the same period showed a 4.5 percent increase in milk/acre from commercial fertilizer compared to 8.4 percent increase in milk/acre from manure application when compared to non-fertilized checks.